The present invention relates to a filter element comprising at least one flat element wrapped into a compact body through which fluid to be filtered flows axially between its two axial end faces, and which has at least one continuous main sealing ring around its outer periphery arranged adjacent the end face on the intake side.
German Patent Publication No. DE 32 49 151 C2 discloses a compact air filter element. This filter element is formed of a corrugated or pleated filter paper and a smooth filter paper. The filter papers are bonded together and then tightly wrapped together to form a filter element of the desired size. Bonding is effected by applying bands of adhesive in the margin such that intervening spaces between the corrugated and the smooth layer are alternately closed at the two end faces to prevent direct flow through the channels formed between the filter papers. A fluid stream, particularly air taken in by an internal combustion engine and flowing from the unfiltered air side to the filtered air side flows initially only into a dead-end channel, then through the filter paper and out of a dead-end channel on the other side. Compared to conventional pleated filters, these compact air filters have the advantage of offering either a larger filter surface for the same overall size or the same filter surface in a smaller overall size.
In round filters in which the outer circumference is the intake side or the unfiltered air side, the outside air that is taken in must still pass the filter medium even if the filter housing is damaged. In axial flow filters, there is a problem that if a stone, for example, strikes and damages an external filter housing of a commercial vehicle or if a dropped tool damages the air filter housing, the filter element may be bypassed so that dirt-laden unfiltered air enters a downstream internal combustion engine. Because compact air filters usually have a circumferential sealing collar that is formed onto the body of the filter near an end face, by which the unfiltered air side is separated from the filtered air side, the major part of the length of the compact air filter element is located on the filtered side of the housing. If the housing is damaged, dirt can flow unhindered through the gap between the housing and the air filter element to the filtered air connection. This can damage the downstream consumer, such as an internal combustion engine.